Pressure sensors are generally known, and are used for pressure sensing in harsh media, in high-pressure applications such as engine oil, engine transmission, braking systems, refrigerant systems, and fuel injection systems.
In industry today, high pressure sensors are typically made up of a metal or other high strength material to make a high pressure vessel or port that has a specially designed diaphragm integrated into or attached to the port. There is also an opening to allow fluid pressure to enter and a channel for the fluid to pass thru to enter into the diaphragm pressure vessel. The diaphragm is the part of the mechanical structure which is used to turn fluid pressure into a mechanical stress by means of the physical geometry and materials used. Typically, a diaphragm is an area of a pressure vessel which is structurally weakened in order to allow for slight deflection or a concentration of stresses. Mechanical stress is then measured by a sensing element, such as a piezo resistive strain gauge, which is physically bonded to the diaphragm to vary an electrical signal proportional to the mechanical stress in the diaphragm, which can then be conditioned and tuned via an ASIC (Application Specific Integrated Circuit) to generate an electronic pressure sensor output. The sense element is typically located on the outside of the pressure vessel diaphragm, especially in conditions where the media which is creating the pressure may cause damage to electronics, such as those which make up the pressure sensing element or signal conditioning ASIC.
Current high pressure sensor designs are limited in a number of ways. One limitation is that a port and diaphragm combined together and made of a single piece requires the pressure access hole or aperture be equal to or larger than the sensing diaphragm for designs when the diaphragm is oriented perpendicular to the axis of the bore. The access hole being larger than the diaphragm when the diaphragm is perpendicular to the axis of the bore negatively impacts pressure sensitivity, mounting interface size, and parametric performance. This limits the design such that the port opening size is always dictated by the diaphragm size or vice versa for pressure ports with diaphragms which are oriented perpendicular to the axis of the bore.
Another limitation is that a combined port and diaphragm made of multiple pieces requires welding, brazing, or some other joining process. A multiple piece port does address pressure sensitivity, and mounting interface size, but negatively impacts cost, sensor reliability due to extra components and joining processes. These joining processes are complicated, costly, or may not be robust enough to meet strength and fatigue requirements for high pressure applications. Joints may be weak areas, which may fail when exposed to pressure.
Accordingly, there exists a need for a jointless pressure sensor which is less costly to manufacture, satisfies various strength and durability requirements, and is flexible enough in design for use in different applications.